1. Field of the Invention
One aspect of the present invention relates to a signal processing apparatus in which the intelligibility of a signal, such as speech, music, or audio, is improved.
2. Description of the Related Art
When a signal, such as speech, music, or audio, is reproduced, due to the influence of ambient noises other than a predetermined sound (hereinafter, referred to as a target signal), such as speech, music, or audio, the intelligibility of the target signal may be degraded. In order to improve the intelligibility of the target signal, there is a need to perform a signal process according to the ambient noise that is included in the collection signal. In the past, as such a signal processing method, there is disclosed a scheme using the volume level of the ambient noise and a scheme using the frequency characteristics of the ambient noise (s ee JP-A-2001-188599, for instance).
However, since the target signal and the ambient noise are different from each other in the limited frequency band, the frequency bands in which signal components exist may be different from each other or sampling frequencies may be different from each other. In these cases, since the volume level or the frequency characteristics of the ambient noise is not obtained with high accuracy by the related signal processing apparatuses, there is a problem that there is degradation in sound quality and the intelligibility cannot be improved.
In addition, even though the bandwidth of the collected ambient noise is extended using the related technique in which the bandwidth of the target signal, such as speech signals, or music and audio signals, is extended using aliasing, a non-linear function, or linear prediction analysis, there is a problem that the frequency characteristics of the ambient noise cannot be estimated with high accuracy.